The cleaning of semiconductor wafers and other substrates has, for a number of years, been accomplished with the use of ultrasonic energy when the wafers or substrates are immersed in a cleaning solution. Disclosures of ultrasonic cleaners of this type are found U.S. Pat. Nos. 2,760,501, 2,828,231, 2,985,003, 3,527,607 and 3,640,295. Additional disclosures covering cleaning systems using energy in the megasonic range include U.S. Pat. Nos. 3,893,869, 4,099,417, 4,118,649, 4,326,553 and 4,543,130. Japanese patent application No. 46-7105, published Mar. 12, 1971, also discloses an ultrasonic cleaning device for flat substrate members, such as semiconductor wafers.
In some of the foregoing disclosures, the substrates are flat in shape and are oriented with respect to the ultrasonic energy so that the energy will cause effective cleaning of as much of the exposed surface of each substrate as possible. While the prior art apparatus and methods for cleaning articles of this type have been satisfactory for the most part, there is still need for improvements in the cleaning of such substrates as well as improvements in the drying of the substrates. These improvements are necessary to minimize production costs, and to provide a higher degree of cleanliness and dryness of the substrates so that they will be immediately ready for further processing, all of which is to be accomplished in a minimum of process time and at minimum expense to reduce the cost of manufacture of the products formed from the substrates themselves.